Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=true), and the description adds non-obvious requirements not in the schema: an Indie plan (trials count) and an authorized account or write-scope API key. This is genuine additional context beyond structured fields.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences: the action and its ordering behavior come first, followed by prerequisites. Every clause earns its place with no redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple two-parameter append tool with no output schema, the description covers action, ordering, prerequisites, and auth. An agent has enough to invoke it correctly, though it doesn't describe the resulting state or any limits on set size.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so both parameters (set_id and layout) are already documented, including the 'omit for a blank screen' hint. The description adds nothing parameter-specific, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a precise verb (append) and resource (a screen to a screenshot set), with the append-at-end semantics made explicit. It also names the sibling sonar_update_screenshot_set for reordering, clearly distinguishing it from create/update/delete screenshot tools.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explains that the new screen is appended at the end and points to sonar_update_screenshot_set when reordering is needed, which is useful routing. It does not, however, state when to prefer this over creating a new set or other alternatives explicitly.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.